A system of this kind for operating an internal combustion engine having direct injection especially for a motor vehicle is generally known and is continuously further developed with respect to a further reduction of fuel and a reduction of exhaust gas.
In this connection, a so-called stratified charge operation as a first operating mode and a so-called homogeneous operation as a second operating mode are distinguished. The stratified charge operation is especially used for small loads; whereas, the homogeneous operation is applied for larger loads applied to the engine. In the stratified charge operation, the fuel is injected into the combustion chamber during the combustion phase and is there injected in the immediate vicinity of a spark plug. The fuel can however also be injected further distant from the spark plug and can be conducted to the spark plug via a movement of air. This has the consequence that no uniform distribution of the fuel can take place in the combustion chamber. The advantage of the stratified operation is that the applied smaller loads can be handled by the engine with a very small quantity of fuel. Larger loads, however, cannot be satisfied in the stratified charge operation. In the homogeneous operation, which is provided for such larger loads, the fuel is injected during the intake phase of the engine so that a swirling and therefore a distribution of the fuel in the combustion chamber can still easily take place. To this extent, the homogeneous operation corresponds approximately to the operation of internal combustion engines wherein fuel is injected into the intake manifold in the conventional manner.
In both modes of operation, that is, in the stratified load operation and in the homogeneous operation, the fuel quantity to be injected is controlled (open loop and/or closed loop) to an optimal value in dependence upon a plurality of input quantities with respect to a reduction of fuel, a reduction of exhaust gas and the like.
Here it is advantageous for the reduction of the generated exhaust gas when the exhaust, which arises in the combustion in the combustion chambers, is not immediately discharged into the ambient and is instead fed back into the combustion chambers in order to again be conducted for combustion.